1. Field of the Invention
The present invention relates to an optical scanning apparatus and an image forming apparatus using it, and, more particularly, to the apparatus constructed in such structure that in formation of an image with a plurality of light beams, a detecting means comprised of a single sensor detects environmental variation of the optical scanning apparatus, particularly, deviation of scanning positions and variation of magnification occurring with temperature changes, and that drawing positions of the light beams on a scanned surface are corrected based thereon, thereby obtaining a good image.
2. Related Background Art
FIG. 1 is a schematic diagram of a major part of a conventional optical scanning apparatus using a multi-laser light source.
In the same figure a plurality of (two in the same figure) light beams (nearly parallel beams) emitted from laser unit 131 are incident into a cylindrical lens 132 having a predetermined refracting power in the sub-scanning direction. The nearly parallel beams incident into the cylindrical lens 132 emerge as nearly parallel beams in the principal scanning section. In the sub-scanning section they converge to be focused as almost line images on a deflecting face (reflecting surface) 133a of optical defector 133. The plurality of light beams deflected and reflected by the deflecting face 133a are condensed through imaging means (fxcex8 lens system) 140 having spherical lens 134 and toric lens 135, onto the surface of a photosensitive drum 136. With rotating the optical deflector 133 in the direction of arrow A, the plurality of light beams scan the area on the surface of the photosensitive drum 136 at constant speed in the direction of arrow 8 (in the main scanning direction). This effects recording of an image on the surface of photosensitive drum 136 being a recording medium. Although the laser unit 131 emits the two light beams, only one of them is illustrated in FIG. 1.
A color image forming apparatus such as a full color printer or the like for multi-color development by use of a plurality of such optical scanning devices described above is suggested, for example, in Japanese Laid-open Patent Application No. 1-281468. The application describes the apparatus for forming a color image by multiply transferring images obtained by the respective optical scanning devices onto a recording medium. In the apparatus of the application, in order to prevent chromatic deviation occurring upon superposition of the images on the recording medium, a detecting means detects positions of detected images drawn on a transfer medium conveyed on a transfer belt in each of the optical scanning devices and the chromatic deviation is prevented by controlling image forming portions according to output signals from the detecting means.
The apparatus of the above application, however, had such tendencies that the structure of the detecting means became complicated and could not easily effect the detection in real time. Further, the application disclosed nothing about a method for detecting the environmental variation of each optical scanning device, particularly, about a method for detecting deviation of the scanning positions, variation of magnification of the optical system, etc. occurring with temperature change.
An object of the present invention is to provide an optical scanning apparatus having a multi-laser light source, capable of obtaining a good image by such structure that simple detecting means, including a single sensor, detects the deviation of the scanning positions and the variation of magnification, and that correcting means corrects image deviation based on the result of the detection, and also provides an image forming apparatus using it.
Another object of the present invention is to provide an optical scanning apparatus having a multi-laser light source, capable of obtaining a good image by such structure that simple detecting means, including a single sensor, detects the deviation of the scanning positions and the variation of magnification occurring with temperature changes of the apparatus and that correcting means corrects image deviation based on the result of the detection, and also provides an image forming apparatus using it.
An optical scanning apparatus of the present invention is an optical scanning apparatus arranged to guide a plurality of light beams, emitted from light source means having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto a scanned surface by imaging means, and optically scan an area on the scanned surface simultaneously with the plurality of light beams.
The detecting means are arranged on a surface substantially at the same position as the scanned surface and in a normal direction to the main scanning. The plurality of light beams from the light source means via the deflecting means are focused by the imaging means, wherein the detecting means detects scanning positions of the plurality of light beams and differences between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification occurring with temperature changes of the optical scanning apparatus. Correcting means correct drawing positions of the plurality of light beams on the scanned surface, based on the result of the detection.
Another optical scanning apparatus of the present invention is an optical scanning apparatus arranged to guide a plurality of light beams, emitted from light source means having a plurality of light-emitting portions arranged in a normal direction to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto a scanned surface by imaging means, and optically scan an area on the scanned surface simultaneously with the plurality of light beams.
The detecting means are arranged on a surface substantially at the same position as the scanned surface and as inclined with respect to the main scanning direction. The plurality of light beams from the light source means via the deflecting means are focused by the imaging means, wherein the detecting means detects scanning positions of the plurality of light beams and differences between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification occurring with temperature changes of the optical scanning apparatus, and wherein correcting means corrects drawing positions of the plurality of light beams on the scanned surface, based on the result of the detection.
Another optical scanning apparatus of the present invention is an optical scanning apparatus arranged to guide a plurality of light beams emitted from a light source means having a plurality of light-emitting portions, arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto a scanned surface by imaging means, and optically scan an area on the scanned surface simultaneously with the plurality of light beams.
A slit is disposed in front of a detecting means arranged substantially at the same position as the scanned surface and in a normal direction to the main scanning direction. The plurality of light beams from the light source means via the deflecting means are focused on a surface of the detecting means through the slit by the imaging means, and the detecting means detects scanning positions of the plurality of light beams and intensity variation of output signals, thereby detecting deviation of the scanning positions and variation of magnification occurring with temperature changes of the optical scanning apparatus. Correcting means corrects drawing positions of the plurality of light beams on the scanned surface, based on the result of the detection.
The above optical scanning apparatus of the present invention is also characterized in that when at least one of an amount of the deviation of the scanning positions or an amount of the variation of magnification detected by the detecting means reaches a predetermined level, the correcting means corrects the drawing positions of the plurality of light beams on the scanned surface.
The above optical scanning apparatus of the present invention is also characterized in that based on the result of the detection at a predetermined time after power-on of the optical scanning apparatus, the correcting means corrects the drawing positions of the plurality of light beams on the scanned surface.
An image forming apparatus of the present invention uses a plurality of optical scanning devices described above and forms a color image by multiply transferring images obtained by the plurality of optical scanning devices each onto a recording medium.
Another optical scanning apparatus of the present invention is an optical scanning apparatus arranged to guide a plurality of light beams, emitted from light source means having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto a scanned surface by imaging means, and optically scan an area on the scanned surface simultaneously with the plurality of light beams.
The optical scanning apparatus includes detecting means arranged substantially at the same position as the scanned surface and in a normal direction to the main scanning direction. The detecting means detects scanning positions of the plurality of light beams and differences between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification, while the plurality of light beams from the light source means via the deflecting means are focused thereon by the imaging means. The optical scanning apparatus also includes correcting means for correcting drawing positions of the plurality of light beams on the scanned surface, and temperature detecting means provided in the optical scanning apparatus.
The temperature detecting means detects a temperature in the optical scanning apparatus after power-on of the optical scanning apparatus. The correcting means corrects the drawing positions of the plurality of light beams, based on the detection result of the detecting means, in accordance with changes in the temperature detected, or every time the temperature detected reaches a preset temperature.
Another optical scanning apparatus of the present invention is an optical scanning apparatus arranged to guide a plurality of light beams, emitted from light source means having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto a scanned surface by imaging means, and optically scan an area on the scanned surface simultaneously with the plurality of light beams.
The optical scanning apparatus includes detecting means arranged substantially at the same position as the scanned surface and in a normal direction to the main scanning direction. The detecting means detects scanning positions of the plurality of light beams and differences between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification, while the plurality of light beams from the light source means via the deflecting means are focused thereon by the imaging means. The optical scanning apparatus also includes correcting means for correcting drawing positions of the plurality of light beams on the scanned surface, and time measuring means for measuring a time after power-on of the optical scanning apparatus.
The correcting means corrects the drawing positions of the plurality of light beams, based on the detection result of the detecting means, in accordance with the time measured, or at a preset time.
Another optical scanning apparatus of the present invention is an optical scanning apparatus arranged to guide a plurality of light beams, emitted from light source means having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto a scanned surface by imaging means, and optically scan an area on the scanned surface simultaneously with the plurality of light beams.
The optical scanning apparatus includes detecting means arranged substantially at the same position as the scanned surface and as inclined with respect to the main scanning direction. The detecting means detects scanning positions of the plurality of light beams and differences between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification, while the plurality of light beams from the light source means via the deflecting means are focused thereon by the imaging means. The optical scanning apparatus also includes correcting means for correcting drawing positions of the plurality of light beams on the scanned surface, and temperature detecting means provided in the optical scanning apparatus.
The temperature detecting means detects a temperature in the optical scanning apparatus after power-on of the optical scanning apparatus. The correcting means corrects the drawing positions of the plurality of light beams based on the detection result of the temperature detecting means in accordance with changes in the temperature detected, or every time the temperature detected reaches a preset temperature.
Another optical scanning apparatus of the present invention is an optical scanning apparatus arranged to guide a plurality of light beams, emitted from light source means having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto a scanned surface by imaging means, and optically scan an area on the scanned surface simultaneously with the plurality of light beams.
The optical scanning apparatus includes detecting means arranged substantially at the same position as the scanned surface and as inclined with respect to the main scanning direction. The detecting means detects scanning positions of the plurality of light beams and differences between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification, while the plurality of light beams from the light source means via the deflecting means are focused thereon by the imaging means. The optical scanning apparatus also includes correcting means for correcting drawing positions of the plurality of light beams on the scanned surface, and time measuring means for measuring a time after power-on of the optical scanning apparatus.
The correcting means corrects the drawing positions of the plurality of light beams based on the detection result of the detecting means, in accordance with the time measured, or at a preset time.
Another optical scanning apparatus of the present invention is an optical scanning apparatus arranged to guide a plurality of light beams, emitted from light source means having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto a scanned surface by imaging means, and optically scan an area on the scanned surface simultaneously with the plurality of light beams.
The optical scanning apparatus includes detecting means arranged substantially at the same position as the scanned surface and in a normal direction to the main scanning direction. The detecting means detects scanning positions of the plurality of light beams and intensity variation of output signals, thereby detecting deviation of the scanning positions and variation of magnification, while the plurality of light beams from the light source means via the deflecting means are focused thereon by the imaging means through a slit disposed in front of the detecting means. The optical scanning apparatus also includes correcting means for correcting drawing positions of the plurality of light beams on the scanned surface, and temperature detecting means provided in the optical scanning apparatus.
The temperature detecting means detects a temperature in the optical scanning apparatus after power-on of the optical scanning apparatus. The correcting means corrects the drawing positions of the plurality of light beams based on the detection result of the temperature detecting means, in accordance with changes in the temperature detected, or every time the temperature detected reaches a preset temperature.
Another optical scanning apparatus of the present invention is an optical scanning apparatus arranged to guide a plurality of light beams, emitted from a light source means having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto a scanned surface by imaging means, and optically scan an area on the scanned surface simultaneously with the plurality of light beams.
The optical scanning apparatus includes detecting means arranged substantially at the same position as the scanned surface and in a normal direction to the main scanning direction. The detecting means detects scanning positions of the plurality of light beams and intensity variation of output signals, thereby detecting deviation of the scanning positions and variation of magnification, while the plurality of light beams from the light source means via the deflecting means are focused thereon by the imaging means through a slit disposed in front of the detecting means. The optical scanning apparatus also includes correcting means for correcting drawing positions of the plurality of light beams on the scanned surface, and time measuring means for measuring a time after power-on of the optical scanning apparatus.
The correcting means corrects the drawing positions of the plurality of light beams, based on the detection result of the detecting means, in accordance with the time measured, or at a preset time.
Another image forming apparatus of the present invention is characterized by forming an image by transferring an image formed by use of the optical scanning apparatus described above onto a recording medium.
Another image forming apparatus of the present invention is characterized by using a plurality of optical scanning devices as described above and forming a color image by transferring each of the images obtained by the plurality of optical scanning devices onto a recording medium.
Another image forming apparatus of the present invention is an image forming apparatus arranged to guide a plurality of light beams, emitted from a light source means having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto an image carrier surface, and optically scan an area on the image carrier surface simultaneously with the plurality of light beams.
The image forming apparatus includes detecting means arranged substantially at the same position as the image carrier surface and in a normal direction to the main scanning direction. The detecting means detects scanning positions of the plurality of light beams and differences between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification, while the plurality of light beams from the light source means by the deflecting means are focused thereon by the imaging means. The image forming apparatus also includes correcting means for correcting drawing positions of the plurality of light beams on the image carrier surface, and number-of-printed-sheets calculating means for calculating a number of printed sheets after power-on of the image forming apparatus.
Based on a signal from the number-of-printed-sheets calculating means and the detection result of the detecting means, the correcting means corrects the drawing positions of the plurality of light beams.
Another image forming apparatus of the present invention is an image forming apparatus arranged to guide a plurality of light beams, emitted from a light source means having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto an image carrier surface, and optically scan an area on the image carrier surface simultaneously with the plurality of light beams.
The image forming apparatus includes detecting means arranged substantially at the same position as the image carrier surface and inclined with respect to the main scanning direction. The detecting means detects scanning positions of the plurality of light beams and differences between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification, while the plurality of light beams from the light source means by the deflecting means are focused thereon by the imaging means. The image forming apparatus also includes correcting means for correcting drawing positions of the plurality of light beams on the image carrier surface, and number-of-printed-sheets calculating means for calculating a number of printed sheets after power-on of the image forming apparatus.
Based on a signal from the number-of-printed-sheets calculating means and the detection result of the detecting means, the correcting means corrects the drawing positions of the plurality of light beams.
Another image forming apparatus of the present invention is an image forming apparatus arranged to guide a plurality of light beams, emitted from light source means having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto an image carrier surface, and optically scan an area on the image carrier surface simultaneously with the plurality of light beams.
The image forming apparatus includes detecting means arranged substantially at the same position as the image carrier surface and in a normal direction to the main scanning direction. The detecting means detects scanning positions of the plurality of light beams and intensity variation of output signals, thereby detecting deviation of the scanning positions and variation of magnification, while the plurality of light beams from the light source means via the deflecting means are focused thereon by the imaging means through a slit disposed in front of the detecting means. The image forming apparatus also includes correcting means for correcting drawing positions of the plurality of light beams on the image carrier surface, and number-of-printed-sheets calculating means for calculating a number of printed sheets after power-on of the image forming apparatus.
Based on a signal from the number-of-printed-sheets calculating means and the detection result of the detecting means, the correcting means corrects the drawing positions of the plurality of light beams.
A further optical scanning apparatus of the present invention is an optical scanning apparatus arranged to guide a plurality of light beams, emitted from a light source means having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto a scanned surface by imaging means, and optically scan an area on the scanned surface simultaneously with the plurality of light beams.
The detecting means are arranged on a surface substantially at the same position as the scanned surface and in a normal direction to the main scanning direction. The plurality of light beams from the light source means by the deflecting means are focused by the imaging means. The detecting means detects scanning positions of the plurality of light beams and differences between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification of the optical scanning apparatus. The correcting means corrects drawing positions of the plurality of light beams on the scanned surface, based on the result of the detection.
Another optical scanning apparatus of the present invention is an optical scanning apparatus arranged to guide a plurality of light beams, emitted from a light source means having a plurality of light-emitting portions arranged in a normal direction to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means, onto a scanned surface by imaging means, and optically scan an area on the scanned surface simultaneously with the plurality of light beams.
The detecting means are arranged on a surface substantially at the same position as the scanned surface and inclined with respect to the main scanning direction. The plurality of light beams from the light source means via the deflecting means are focused by the imaging means. The detecting means detects scanning positions of the plurality of light beams and differences between pass times of the plurality of light beams, thereby detecting deviation of the scanning positions and variation of magnification of the optical scanning apparatus. The correcting means corrects drawing positions of the plurality of light beams on the scanned surface, based on the result of the detection.
Another optical scanning apparatus of the present invention is an optical scanning apparatus arranged to guide a plurality of light beams, emitted from a light source means having a plurality of light-emitting portions arranged as inclined with respect to a main scanning direction, to a deflecting means, guide the plurality of light beams deflected and reflected by the deflecting means onto a scanned surface by imaging means, and optically scan an area on the scanned surface simultaneously with the plurality of light beams.
A slit is disposed in front of the detecting means arranged substantially at the same position as the scanned surface and in a normal direction to the main scanning direction. The plurality of light beams from the light source means via the deflecting means are focused on a surface of the detecting means through the slit by the imaging means. The detecting means detects scanning positions of the plurality of light beams and intensity variation of output signals, thereby detecting deviation of the scanning positions and variation of magnification of the optical scanning apparatus. Correcting means corrects drawing positions of the plurality of light beams on the scanned surface based on the result of the detection.
The above optical scanning apparatus of the present invention is also characterized in that when at least one of an amount of the deviation of the scanning positions or an amount of the variation of magnification detected by the detecting means reaches a predetermined level, the correcting means corrects the drawing positions of the plurality of light beams on the scanned surface.
The above optical scanning apparatus of the present invention is also characterized in that based on the result of the detection at a predetermined time after power-on of the optical scanning apparatus, the correcting means corrects the drawing positions of the plurality of light beams on said scanned surface.
A further image forming apparatus of the present invention uses a plurality of optical scanning devices described above and forms a color image by multiply transferring images obtained by a plurality of optical scanning devices each onto a recording medium.